Once upon a time I ran with Turner spacers, 12.5mm front and rear. It improved the stance and closed the gap a bit, more noticeable on the rear. I also had MS 12r, 15f on my last M3. I didn't have any issues with either brand. The Turner's are machined beautifully, they'd be my choice. Here's some old pics with the Turner 12.5mm's to give you an idea, stock suspension.